1. Field of the Invention
The present invention relates to a zoom lens system.
2. Description of the Prior Art
A single-lens reflex camera has been well known which is structured so that the user views through the finder a luminous flux having passed through the zoom lens system and reflected by a reflecting mirror (hereinafter, referred to as TTL (through-the-lens) mirror). In the conventional single-lens reflex camera, the TTL mirror and the shutter are disposed between the zoom lens system and the image receiving plane such as film or a light receiving device. That is, in the conventional single-lens reflex camera, space for the TTL mirror and the shutter is necessary between the zoom lens system and the image receiving plane. This has been an obstacle to the size reduction of the single-lens reflex camera.
A conceivable way to reduce the size of the single-lens reflex camera is to incorporate in the zoom lens system the shutter which is disposed between the zoom lens system and the image receiving plane in the conventional single-lens reflex camera.
By doing so, the size of the single-reflex camera may be reduced because only space for the TTL mirror is necessary between the zoom lens system and the image receiving plane. However, the conventional zoom lens system is designed to have a back focal length (the distance between the vertex of the most image side surface of the lens system and the image plane) suitable for the conventional single-lens reflex camera where the TTL mirror and the shutter are disposed between the zoom lens system and the image receiving plane. For this reason, by merely incorporating the shutter in the zoom lens system, the distance between the zoom lens system and the image receiving plane cannot be reduced, so that the size reduction of the single-lens reflex camera cannot be achieved.